ruby sort_by method

Question

I have just started to learn ruby. I have an array of hashes. I want to be able to sort the array based on an elementin the hash. I think I should be able to use the sort_by method. Can somebody please help?

#array of hashes
array = []
hash1 = {:name => "john", :age => 23}
hash2 = {:name => "tom", :age => 45}
hash3 = {:name => "adam", :age => 3}
array.push(hash1, hash2, hash3)
puts(array)

Here is my sort_by code:

# sort by name
array.sort_by do |item|
    item[:name]
end
puts(array)

Nothing happens to the array. There is no error either.

steenslag · Accepted Answer · 2013-01-01 20:38:10Z

43

You have to store the result:

res = array.sort_by do |item|
    item[:name]
end 
puts res

Or modify the array itself:

array.sort_by! do |item| #note the exclamation mark
    item[:name]
end 
puts array

edited Jan 1, 2013 at 20:38

answered Jan 1, 2013 at 20:24

steenslag

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2 Comments

U-L Over a year ago

Thank you. I just also figured out the same. Saw another sort_by example. So sort_by does not do inplace.

quandrum Over a year ago

Bang methods (Those ending with !) modify in place, but it's good practice to not use them and create new objects as modified versions of old ones. Subtle bugs can be introduced into your programs by allowing methods to mutate your objects.

ray · Accepted Answer · 2018-11-27 09:37:16Z

1

You can do it by normal sort method also

array.sort { |a,b| a[:name] <=> b[:name] }

Above is for ascending order, for descending one replace a with b. And to modify array itself, use sort!

answered Nov 27, 2018 at 9:37

ray

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Comments

Joshua Pinter · Accepted Answer · 2025-02-25 17:44:04Z

1

You can use sort_by! method in one line:

array.sort_by!{|item| item[:name]}

This will mutate the original array object.

edited Feb 25 at 17:44

Joshua Pinter

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answered Nov 27, 2018 at 9:30

Saravanan Kothandapani

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1 Comment

mechnicov Feb 25 at 18:08

It repeats accepted answer

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